Abstract: As one of the key issues of regional respond to global climatic change, the sustainability of agricultural production under the changing climate is attracting more and more academic focuses. The impact of climate change on the agriculture results from the change of climate elements mean values and of the climate variability. The assessment system of winter wheat water and yield in the Huang-Huai-Hai Plain, the main production area of food in China, is submitted in this paper to discuss the impact of climate variability and future climate on the production of wheat. The system is made up with a set of models, which is based on the following idea. Crop uses water in the form of the transference of precipitation, soil moisture and plant water. The situation of crop water supply and requirement can be expressed by the relationship between actual evaportranspiration and potential evaportranspiration. Then we can estimate crop yield from the loss of evaportranspiration. The simulation of water balance during the growth period of winter wheat shows that the deficience of water are 200400 mm in the area of north of the Yellow River, 100 mm or so in the middle part of the Plain, and nearly zero in the area including south of Henan province, north of Anhui and Jiangsu province. The spatial divergence of irrigation amount is discussed, too. From the water balance estimation model, the yield of winter wheat can be calculated under the scenario of climate change in the future. So the change of yield of winter wheat in the Plain in the future is given, which is yield decrease in the most part of the plain.